1. Field of the Invention
The present invention relates to a laser-scanning examination apparatus.
This application is based on Japanese Patent Application No. 2004-217605, the content of which is incorporated herein by reference.
2. Description of Related Art
Known apparatuses in the related art for observing cellular function and the like by irradiating a specimen, such as a living organism, from the surface thereof with excitation light and detecting fluorescence generated at a comparatively deep position below the surface of the specimen include multiphoton-excitation-type examination apparatuses (see, for example, Japanese Unexamined Patent Application Publication No. 2002-243641, page 3, etc.).
This multiphoton-excitation-type examination apparatus has a configuration in which fluorescence emitted from the specimen is detected by an external photomultiplier tube that is connected via a single-mode fiber.
However, the single-mode fiber suffers from the drawback that it is not possible to carry out measurement efficiently because the core diameter is narrow and thus fluorescence returning from the specimen is spatially confined. In order to more efficiently measure the fluorescence, it is preferable to dispose the photomultiplier tube directly after the objective lens in the measurement head; in such a case, however, since the photomultiplier tube is comparatively large, the measurement head itself becomes larger and therefore is not suitable for use in applications where it needs to be disposed at various orientations and positions according to the examination site in the specimen, for example, when carrying out in-vivo examination of small laboratory animals.
On the other hand, a multimode fiber has been considered for use as an optical fiber that has a large core diameter and thus does not confine the fluorescence from the specimen; however, light of multiple transmission modes propagates in multimode fibers. As a result, when ultrashort-pulse laser light from a laser light source is introduced thereto, multiple mode splitting occurs, which increases the pulse width. Such light has a drawback in that it is not possible to efficiently generate the multiphoton-excitation effect.